How does launch control help acceleration

[David Bennett]

OK so bear with me on this. I’ve had a glass or two of barolo so might not be thinking straight.

So if LC only lasts 2.5 seconds and peak torque does not change just how is LC beneficial. Surely on launch it takes a second or two to gain enough revs to generate peak power (A bit quicker on the rear axle with the shorter first gear) and by the time you can generate the power the LC window is much reduced. Obviously it works if the reviews are to be believed but can anyone add anything on the real benefits?

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[Jhenson29]

Who said torque doesn’t change? I don’t see how it can’t.

The overboost Is almost certainly allowing a higher current which will translate to more torque.

There’s only so many variables to work with here.

 

[OTPSkipper]

OK so bear with me on this. I’ve had a glass or two of barolo so might not be thinking straight.

So if LC only lasts 2.5 seconds and peak torque does not change just how is LC beneficial. Surely on launch it takes a second or two to gain enough revs to generate peak power (A bit quicker on the rear axle with the shorter first gear) and by the time you can generate the power the LC window is much reduced. Obviously it works if the reviews are to be believed but can anyone add anything on the real benefits?

Sync motors don’t need to build rpm to get torque. They pull from 0 rpm. This is why diesel trains have electric drive. I think the LC just gets the full current into the motor faster. For example, it dosnt have to wait for the accelerator peddle to move. Even if you stomp on it, that is still 100msec for the peddle to travel the whole way. Then there is probably some electronic accelerator smoothing on top of that. That could be another 200msec of delay to max torque.
With launch control, they can use a code path in the SW that is pumping max torque that dosnt spin the wheels right off the bat when they sense the brake release.
Anyway. That is my educated guess.

 

[Jhenson29]

I think the LC just gets the full current into the motor faster.

LC has a claimed increase in HP that this explanation would not account for. Rate of change of current/torque would not change peak HP.

 

[OTPSkipper]

LC has a claimed increase in HP that this explanation would not account for. Rate of change of current/torque would not change peak HP.

Could be both affects.

 

[David Bennett]

Yeah I get that but power is torque * revs and revs take time to build. It’s the power that results in performance. Even if you get instant torque you don’t get instant max power. Maybe Jenson29 is right and torque is boosted. I‘ve not seen any data on that though…..

 

[OTPSkipper]

Torque makes acceleration. Power allows higher speed.

 

[W1NGE]

Isn't it just simply the case that access (temporarily) to full power of the motors and battery is made available i.e. the flood gates are let wide open?

 

[OTPSkipper]

Yeah I get that but power is torque * revs and revs take time to build. It’s the power that results in performance. Even if you get instant torque you don’t get instant max power. Maybe Jenson29 is right and torque is boosted. I‘ve not seen any data on that though…..

I think @Jhenson29 is correct too. I think they can dump more current in for a short amount of time during LC to make more power and torque.

 

[Jhenson29]

Yeah I get that but power is torque * revs and revs take time to build. It’s the power that results in performance. Even if you get instant torque you don’t get instant max power. Maybe Jenson29 is right and torque is boosted. I‘ve not seen any data on that though…..

Torque is what controls your acceleration rate at any given time.

And, if torque is boosted and maintained through the constant torque range, then max HP is boosted also.

And, from Taycan 4S specs (as an example), max torque is called out with launch control. I’m not sure why they would do it that way if there was no difference.

 

[philbur]

I use it to dry the car after washing it.. leaves a puddle the shape of the car and then just have to do some minor drying!

 

[Jhenson29]

Isn't it just simply the case that access (temporarily) to full power of the motors and battery is made available i.e. the flood gates are let wide open?

I don’t think so. OP is asking how it does it without more torque. There’s a callout for a specific max HP increase with overboost, so where does this come from? I’m suggesting an increased current limit, as it is on every electric motor I’ve ever worked with. The only other way I think it could even be done is to increase voltage above base RPM, but A) I don’t know that the batteries could provide that and B) it doesn’t do anything below base speed and C) I’ve never seen any electric motor controlled that way.

Again…only so many variables.

 

[David Bennett]

I think @Jhenson29 is correct too. I think they can dump more current in for a short amount of time during LC to make more power and torque.

If that is true then the max torque quoted is most likely LC torque. Has anybody seen any non LC torque figures?

 

[OTPSkipper]

Isn't it just simply the case that access (temporarily) to full power of the motors and battery is made available i.e. the flood gates are let wide open?

I think they are shaping the torque curve to fit the traction available for LC. This can easily be done with the kind of motor in the Taycan.

 

[Jhenson29]

If that is true then the max torque quoted is most likely LC torque.

Correct, see above picture.

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